[dpdk-dev] Polling too often at lower packet rates?
Paul Emmerich
emmericp at net.in.tum.de
Fri Apr 10 02:42:46 CEST 2015
Stephen Hemminger <stephen at networkplumber.org> wrote:
> Your excess polling consumes PCI bandwidth which is a fixed resource.
I doubt that this is the problem for three reasons:
* The poll rate would regulate itself if the PCIe bus was the bottleneck
* This problem only occurs with 82599 chips, not with X540 chips
(which are virtually identical except for 10GBase-T vs. fiber)
* This effect already appears with relatively low poll rates (batch size 1).
The overhead would have to be > 128 bytes per poll to saturate the PCIe bus
at this rate. (Even if this was the case, my first point still applies)
I unfortunately don't have a test system with a CPU that supports PCIe
performance counters with a 82599 card. Otherwise I'd measure this since I
think this effect is really interesting (I'm a co-authors of the paper
linked above).
Paul
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